期刊
ASTRONOMY & ASTROPHYSICS
卷 507, 期 1, 页码 389-396出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/200912339
关键词
radiation mechanisms: non-thermal; methods: observational; stars: binaries: general; stars: neutron; gamma rays: observations; telescopes
资金
- German Ministry for Education and Research (BMBF)
- Max Planck Society
- French Ministry for Research
- CNRS
- UK Science and Technology Facilities Council (STFC)
- IPNP of the Charles University
- Polish Ministry of Science and Higher Education
- South African Department of Science and Technology
- National Research Foundation
- University of Namibia
- CAPES Foundation, Ministry of Education of Brazil
- STFC [ST/F002963/1, ST/G003084/1, PP/E001319/1] Funding Source: UKRI
- Science and Technology Facilities Council [PP/E001319/1, ST/G003084/1, ST/F002963/1] Funding Source: researchfish
Aims. This article presents very-high-energy (VHE; E > 100 GeV) data from the gamma-ray binary PSR B1259-63 as taken during the years 2005, 2006 and before as well as shortly after the 2007 periastron passage. These data extend the knowledge of the lightcurve of this object to all phases of the 3.4 year binary orbit. The lightcurve constrains physical mechanisms present in this TeV source. Methods. Observations of VHE gamma-rays with the HESS telescope array using the Imaging Atmospheric Cherenkov Technique were performed. The HESS instrument features an angular resolution of < 0.1 degrees and an energy resolution of < 20%. Gamma-ray events in an energy range of 0.5-70 TeV were recorded. From these data, energy spectra and lightcurve with a monthly time sampling were extracted. Results. VHE gamma-ray emission from PSR B1259-63 was detected with an overall significance of 9.5 standard deviations using 55 h of exposure, obtained from April to August 2007. The monthly flux of gamma-rays during the observation period was measured, yielding VHE lightcurve data for the early pre-periastron phase of the system for the first time. No spectral variability was found on timescales of months. The spectrum is described by a power law with a photon index of Gamma = 2.8 +/- 0.2(stat) +/- 0.2(sys) and flux normalisation Phi(0) = (1.1 +/- 0.1(stat) +/- 0.2(sys)) x 10(-12) TeV-1 cm(-2) s(-1). PSR B1259-63 was also monitored in 2005 and 2006, far from periastron passage, comprising 8.9 h and 7.5 h of exposure, respectively. No significant excess of.-rays is seen in those observations. Conclusions. PSR B1259-63 has been re-confirmed as a variable TeV gamma-ray emitter. The firm detection of VHE photons emitted at a true anomaly theta approximate to -0.35 of the pulsar orbit, i.e. already similar to 50 days prior to the periastron passage, disfavors the stellar disc target scenario as a primary emission mechanism, based on current knowledge about the companion star's disc inclination, extension, and density profile.
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